Electronic devices typically include a variety of common circuit components, including passive components such as resistors, inductors, and capacitors, as well as active components such as transistors and integrated circuits. Passive components such as inductors or capacitors are designed to store energy, and resistors are designed to resist the flow of applied current to a specified degree. Most capacitors comprise conductive plates separated by an insulator and are configured to provide a specified opposition to change in voltage across the plates.
In practical applications, passive components may not have only those desired electrical characteristics described above. For example, a capacitor may exhibit some amount of effective inductance and resistance. Although it is difficult to measure the resistance or inductance present across a capacitor because it includes a nonconductive layer, various methods of measuring and calculating an equivalent series inductance (ESL) and an equivalent series resistance (ESR) of a capacitor have been developed and are useful in characterizing capacitors. Equivalent series inductance is also sometimes called parasitic inductance, indicating that although it is present it is not generally desired.
In conventional capacitors, it is difficult to provide both high equivalent series resistance (ESR) and low equivalent series inductance (ESL).